Liquid scintillator (LS) has been used to detect reactor antineutrinos since 1950s [1]}. The hydrogen-rich LS serves as both the electron antineutrino target and the active detection material. In the classic detection channel, a reactor antineutrino produces a positron and a neutron via Inverse Beta decay (IBD) reaction, \(\bar{\nu }_e \ + \ p \rightarrow e^+ \ + \ n \) . The positron energy measured with scintillation light is an excellent proxy for the antineutrino energy. The best energy resolutions achieved by large-scale LS detectors are \(6.4\%/\sqrt{E(\mathrm {MeV})}\)  (\(\sim 300\)  p.e./MeV) for the 1-kton KamLAND detector [2]} and \(5\%/\sqrt{E(\mathrm {MeV})}\)  (\(\sim 500\)  p.e./MeV) for the 500-ton Borexino detector [3]}, where p.e. stands for photoelectrons. The 20-kton JUNO detector is designed with an energy resolution of \(3\%/\sqrt{E(\mathrm {MeV})}\)  (\(\sim 1200\)  p.e./MeV) [4]}, almost the limit of conventional technology with photomultipliers (PMTs).
